Both clinical and experimental observations indicate that the cerebellum plays a critical role in both the initiation of a voluntary movement and in the control of its amplitude and speed. It has been shown, in preliminary work using cats trained to perform angular displacements of the elbow joint, that certain cerebellar neuronal activities which may underly these functions begin in advance of the movement and once the motion is in progress are related to the velocity of the motion, most likely as a result of dynamic sensory feedback from the moving part. The aims of the proposed research are to determine if causal relationships exist between this neuronal activity (discharge of neurons of the interpositus nucleus) and parameters of the motion and motor output, and to determine the source and nature of the inputs which produce this neuronal behavior, including the participation of the cerebellar cortex. To this end the changes in discharge rates of neurons in the cerebellar nuclei, cerebellar cortex, and related motor nuclei which occur in relationship to the movement will be recorded along with the displacement itself and the motor output (EMG of biceps and triceps muscles). The experimental variables will include variations in the load conditions under which the movements are made, surgical intervention in the nervous system, and reversible block of cerebellar function by cooling. The data will be analyzed by the use of standard averaging techniques and also certain of the methods of linear systems analysis. Through these efforts, it may be possible to establish that the cerebellum constitutes a system which utilizes both dynamic sensory input derived from an evolving movement and inputs derived from intentional events within the central nervous system to control the motor output.